[PATCH v2 0/2] RDMA/srp: bound the receive IU the target asks for

[Yehyeong Lee]

The target decides how large the initiator's receive buffers are, and the
initiator never checks the answer.

srp_cm_rep_handler() takes max_ti_iu_len out of the SRP_LOGIN_RSP and
srp_alloc_iu_bufs() sizes every receive IU with it. The first patch refuses
a login that reports less than an SRP_RSP, because such a login hands the
receive path undersized buffers, and a report of zero is worse: kzalloc()
answers it with ZERO_SIZE_PTR, which ib_dma_map_single() accepts on a
virtually mapped transport without looking at the length.

The second patch stops srp_recv_done() from syncing those buffers with
ch->max_ti_iu_len. The receive ring is allocated once and kept across a
reconnect while max_ti_iu_len is taken from every login response, so a
target that reports a larger value the second time around makes the driver
sync past the end of the mapping. iu->size is the length that was mapped,
and the length srp_post_recv() posts.

Changes since v1:
1/2 unchanged. Dropped v1 2/2 (drop a truncated SRP_RSP): the floor makes
the buffer always >= sizeof(srp_rsp) so there is no out-of-bounds read, and
dropping the response would lose its req_lim_delta credit (per review). New
2/2 bounds the two srp_recv_done() DMA syncs to iu->size, the reconnect
case review noted 1/2 did not cover.

Yehyeong Lee (2):
  RDMA/srp: refuse a target that cannot receive an SRP_RSP
  RDMA/srp: do not DMA-sync a receive IU past its mapped length

 drivers/infiniband/ulp/srp/ib_srp.c | 11 +++++++++--
 1 file changed, 9 insertions(+), 2 deletions(-)